Provide stubbed visitor implementation

Part of #889

lib/handlebars/compiler/visitor.js

@@ -4,8 +4,64 @@ Visitor.prototype = {
   constructor: Visitor,
 
   accept: function(object) {
-    return this[object.type](object);
-  }
+    return object && this[object.type] && this[object.type](object);
+  },
+
+  program: function(program) {
+    var statements = program.statements,
+        i, l;
+
+    for(i=0, l=statements.length; i<l; i++) {
+      this.accept(statements[i]);
+    }
+  },
+
+  block: function(block) {
+    this.accept(block.mustache);
+    this.accept(block.program);
+    this.accept(block.inverse);
+  },
+
+  mustache: function(mustache) {
+    this.accept(mustache.sexpr);
+  },
+
+  sexpr: function(sexpr) {
+    var params = sexpr.params, paramStrings = [], hash;
+
+    this.accept(sexpr.id);
+    for(var i=0, l=params.length; i<l; i++) {
+      this.accept(params[i]);
+    }
+    this.accept(sexpr.hash);
+  },
+
+  hash: function(hash) {
+    var pairs = hash.pairs;
+
+    for(var i=0, l=pairs.length; i<l; i++) {
+      this.accept(pairs[i][1]);
+    }
+  },
+
+  partial: function(partial) {
+    this.accept(partial.partialName);
+    this.accept(partial.context);
+    this.accept(partial.hash);
+  },
+  PARTIAL_NAME: function(partialName) {},
+
+  DATA: function(data) {
+    this.accept(data.id);
+  },
+
+  STRING: function(string) {},
+  NUMBER: function(number) {},
+  BOOLEAN: function(bool) {},
+  ID: function(id) {},
+
+  content: function(content) {},
+  comment: function(comment) {}
 };
 
 export default Visitor;

spec/visitor.js

@@ -0,0 +1,48 @@
+/*global Handlebars */
+
+describe('Visitor', function() {
+  if (!Handlebars.Visitor) {
+    return;
+  }
+
+  function ast_for(template) {
+    var ast = Handlebars.parse(template);
+    return Handlebars.print(ast);
+  }
+
+  it('should provide coverage', function() {
+    // Simply run the thing and make sure it does not fail and that all of the
+    // stub methods are executed
+    var visitor = new Handlebars.Visitor();
+    visitor.accept(Handlebars.parse('{{#foo (bar 1 "1" true) foo=@data}}{{!comment}}{{> bar }} {{/foo}}'));
+  });
+
+  it('should traverse to stubs', function() {
+    var visitor = new Handlebars.Visitor();
+
+    visitor.PARTIAL_NAME = function(partialName) {
+      equal(partialName.name, 'bar');
+    };
+
+    visitor.STRING = function(string) {
+      equal(string.string, '2');
+    };
+    visitor.NUMBER = function(number) {
+      equal(number.stringModeValue, 1);
+    };
+    visitor.BOOLEAN = function(bool) {
+      equal(bool.stringModeValue, true);
+    };
+    visitor.ID = function(id) {
+      equal(id.original, 'foo.bar');
+    };
+    visitor.content = function(content) {
+      equal(content.string, ' ');
+    };
+    visitor.comment = function(comment) {
+      equal(comment.comment, 'comment');
+    };
+
+    visitor.accept(Handlebars.parse('{{#foo.bar (foo.bar 1 "2" true) [email protected]}}{{!comment}}{{> bar }} {{/foo.bar}}'));
+  });
+});